[v8][gin] Implement CallLowPriorityTaskOnWorkerThread

In https://crrev.com/c/1402790, we introduced a new API function in the
V8 platform API to allow posting of low priority tasks. An example of
such a low priority task is TurboFan compilation for WebAssembly, which
should not delay user-visible tasks like WebAssembly baseline
compilation. This CL is the implementation of that API function in the
gin platform.

R=rmcilroy@chromium.org

Bug: chromium:920181
Change-Id: I798a594a898a9251e0b2c9ebc277864540b9a3e3
Reviewed-on: https://chromium-review.googlesource.com/c/1412461
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624094}
2 files changed